Since Git is not a code mark, Windows is trying to find it against the corps of well-known good (but unsigned) installers. It downloads the entire list of data (and does not send information about what you install to Microsoft.) You can wait (do not restart!) To download this data or disable this scan.
It should be in Settings> Update & Security> Windows Defender. Disable the real-time protection and cloud protection settings, after which you can set them without delay.